This work is being done under four parts. Under Part I, we are seeking to improve both the instrumentation and the biological knowledge involved in improvement of diagnosis and therapy of intracranial tumors by radioisotopic studies. These studies are aimed at the production of isotopes and new compounds, development of instrumentation, the development of computer techniques and the clinical assessment of new methods of diagnosis and therapy. Under Part II, we are studying the growth kinetics and radiation responses of experimental brain tumors, and the variation in these parameters for tumors recurring after the initial radiation treatment. We are also seeking to synthesize chemical compounds and produce antibodies for use in the diagnosis and treatment of intracranial tumors. Radiation sources include the use of x-rays, 60 cobalt radiation and the Harvard Cyclotron. Under Part III, we are assaying the encephalic toxicity of pain relieving agents by the combined use of implanted chemodes and electrodes and behavioral studies in animals and man. Under Part IV, an electron microscopic study of basic structures related to cellular growth and efforts to correlate these with specific functions are under way. We are also examining not only the ultrastructure, but also the effects on growth and metabolism of brain tumors in tissue culture of radiobiological and immunological modalities.